1. Field of the Invention
The present invention relates generally to circuit breakers and, more particularly, to a shock resistant auxiliary switch mechanism for a circuit breaker.
2. Description of the Related Art
Circuit breakers are used for numerous purposes in power distribution systems. Among such purposes is the interruption of current in a protected system during specified conditions.
Each pole of a circuit breaker includes a stationary contact and a movable contact, with the movable contact typically being mounted on an arm that can pivot the movable contact into and out of the electrical engagement with the stationary contact. A multi-pole circuit breaker typically includes a single operating mechanism for all of the poles, with the operating mechanism including a single crossbar and a single cradle. The crossbar extends between all of the poles and synchronizes the operation thereof. The cradle is operable to pivot the crossbar in order to separate the movable contacts from the stationary contacts in the event of a trip situation.
A circuit breaker can be in any one of an ON position, an OFF position, and a TRIPPED position. The movable contacts are connected with the stationary contacts when the circuit breaker is in the ON position. The cradle is a mechanism, usually spring-operated, that is operable to switch the circuit breaker from the ON position to the TRIPPED position by pivoting the crossbar to separate the movable contacts from the stationary contacts. When the cradle is mechanically energized, such as loading the springs thereof, a handle of the circuit breaker can be employed to switch the circuit breaker between the ON position and the OFF position by pivoting the crossbar such that the movable contacts are moved into and out of engagement with the stationary contacts.
While the specific condition of a circuit breaker often is plain to an observer, it is nevertheless often desirable to provide additional apparatuses to indicate to a technician the condition of the circuit breaker. For instance, some circuit breakers include an auxiliary switch that is operated by the crossbar and indicates the condition of the contacts as either being connected or disconnected, meaning that it indicates whether the circuit breaker is in the ON position or is in either of the OFF and TRIPPED positions. Alternatively, or in addition thereto, a circuit breaker may include a bell alarm switch that is operated by the cradle to indicate whether the circuit breaker is in the TRIPPED position or in one of the ON and OFF positions. While such auxiliary switches and bell alarm switches have been generally effective for their intended purposes, such switches have not, however, been without limitations.
Depending upon the application, a circuit breaker may be subjected to shock loading. Different applications have different requirements for the continued operation of circuit breakers during shock loading. Known auxiliary switches typically include a microswitch having a common conductor that is pivotable about an axis, with the pivotable portion having a asymmetric distribution of mass about the pivot point. Such asymmetry can result in unintended rotation of the common conductor in the event of a shock loading, which can undesirably result in an incorrect indication of the condition of the contacts and/or cradle. It is thus desired to provide an improved auxiliary switch mechanism and resulting circuit breaker that are configured to resist the effect of shock loading.